Chemical-mechanical polishing/planarization (CMP) is often implemented in semiconductor devices fabrication. A CMP process can be used for planarizing surfaces of a wafer with a combination of chemical and mechanical forces. Mechanical grinding alone may cause surface damages, while wet etching alone cannot attain good planarization. The CMP process involves both the mechanical grinding and the wet etching to generate a smooth surface on a wafer, and prepare the wafer for subsequent processes (e.g., photolithography) in the fabrication of semiconductor devices.